About the Solar Panel Calculator
Sizing a solar array is the first real step of any rooftop project.
Get it wrong and you either overspend on capacity you never use, or under-build and keep paying the utility.
This calculator turns your monthly bill and local sun hours into a clear system size and panel count.
How this calculator works
We convert your monthly kWh into a daily average, then divide by your location’s peak sun hours and a real-world performance ratio of about 0.78.
That yields the kilowatts of panels required. We divide by your chosen panel wattage to get the number of panels.
Why it matters
- Right-size your system before requesting quotes
- Avoid oversizing and wasted spend
- Understand the roof area you’ll need
- Compare panel wattages instantly
Frequently asked questions
It depends on your electricity use and local sun hours. Most homes need between 12 and 28 panels. Enter your details above for a personalised figure.
It is an hour when solar irradiance averages 1,000 W/m². Sunny regions get 5–6 per day; cloudier climates 3–4.
Higher-wattage panels mean fewer panels for the same output, which helps on smaller roofs.